An ocular lens is used for further magnifying and observing a real image formed by an objective lens, for example, in a telescope, binoculars, a microscope and the like. Such an ocular lens is required to have a sufficient eye relief (on-axis distance between the lens surface, of the ocular lens, that is closest to the viewer's eye side and the eye point) for comfortable observation, and in the nature of things, to correct aberrations across a wide angle of view favorably. However, it is generally well known that the large apparent field of view of the ocular lens causes the eye relief with sufficient length to be difficult to be secured, and the aberrations of light flux in the periphery of the visual field, in particular, the curvature of field and the astigmatism to deteriorate drastically.
Therefore, for example, an ocular lens is disclosed with a configuration in which a negative lens group is disposed on the object side, a positive lens group is disposed on the viewer's eye side, and a field stop is included therebetween (for example, Patent Literature 1). The ocular lens with this kind of configuration disclosed in Patent Literature 1 secures a long eye relief by disposing the negative lens group on the object side. In addition to this, the negative lens group having strong refractive power is included, and thereby, the Petzval sum can be made small, which allows a condition for favorably correcting the curvature of field to be attained. In this type of ocular lens, when the ratio of the focal length of the negative lens group on the object side to the focal length of the positive lens group on the viewer's eye side is closer to 1:1, the Petzval sum can be smaller, and this is advantageous for correction of the curvature of field and the like.